Essential to intestinal epithelial cells (IEC) homeostasis are pattern recognition receptors such as TLR. Upon crossing TLR adapters (e.g., MyD88) ko mice to Apc(Min/+) (Apc) mice, we identified that the genetic deletion of MyD88 in Apc mice (i.e., Apc/MyD88-/- mice) resulted in a significant decrease in IEC tumors and an increase in survival. We observed that the expression levels of c-myc protein in IEC, which controls tumor growth in these mice, were significantly lower than those in Apc mice. We identified that microbial-derived MyD88-dependent TLR ligands enhance c-myc expression in IEC in a Wnt-independent manner by post-translational modifications, mediated by p-ERK. Thus, in SA-1 we will explore whether regulation of p-ERK activity controls intestinal tumorigenesis in Apc mice by genetic and pharmacological means. We will evaluate survival and IEC tumor growth in Apc and Apc/MKP-1-/- (in which MAPK phosphase-1 gene was deleted). We will treat these animals with UO126 (a MEK1/2 inhibitor) and assess the impact of this intervention on survival and IEC tumor growth. We will determine the histopathological features, key signaling events, the expression of the c-myc as well as proliferation and apoptosis of IEC harvested from treated and untreated animals and compare these parameters with those obtained from Apc/MyD88-/- and Apc/c-mycIEC mice (in which c-myc was genetically deleted in IEC). We assume that under inflammatory and in contrast to physiological conditions, TLR-MyD88-independent pathway phosphorylates ERK and therefore increases IEC c-myc levels. Thus, in SA-2, we will treat Apc, and Apc mutants (see above) with the colitis-inducing chemical, DSS, followed by oral administration of UO126 or Sorafenib (a RAS-RAF inhibitor). We will analyze and compare the impact of each drug on survival, IEC tumor induction and IEC biology as described above. This mix of genetic and pharmacological approaches will enable us to better understand the regulation of c-myc expression in IEC and its impact on IEC tumorigenesis. PUBLIC HEALTH RELEVANCE: This grant application proposes to study the impact of innate immunity on IEC tumorigenesis, under inflammatory and non-inflammatory conditions, in the Apc mouse.